This invention relates to the art of supporting the roof of a coal mine or the like and has particular relationship to pin-or-bolt setting for such a roof.
In the interest of safety in the operation of a coal mine, it is essential that the roof of the mine be reliably secured against caving in. To support the roof it is common to insert bolts into the roof. The task of inserting the bolts in the roof is necessarily the most hazardous task involved in a coal mining operation. It is an object of this invention to minimize the hazard involved in roof bolting.
In accordance with the teachings of the prior art, holes are drilled in the roof of the mine and the bolts are inserted in the holes. For this purpose it is necessary that the bolts be of circular section. This practice, in addition to being manual so that it does not lend itself to automation, is highly time consuming; thus, is not only uneconomic, but presents maximum hazard to the personnel involved. It has also been proposed (U.S. Pat. Nos. to Gerald W. Elders, et al, 3,643,542; 3,721,094; 3,734,380; 3,819,101) to drive the bolt into the roof by application of constant force to the bolt. The practice of this proposal requires circularly cylindrical bolts. This approach proved unsatisfactory because the high force demanded bent the bolt instead of driving it into the strata. In addition, the bolt sought the path of least resistance through the strata.
It is an object of this invention to overcome the disadvantages of the prior art and to provide effective apparatus and a method for setting bolts into the roof of a coal mine or the like which apparatus and method shall be economic, shall minimize the hazard of the task of bolt setting and shall readily lend itself to automation.